Encoding of line drawings with a multiple grid chain code

A JBIG-based approach to the encoding of contour maps

Recently, a new technique for the lossless encoding of contour maps was introduced, based on the concept of "transition points". In this paper, we show that by using a simple representation for the transition points, i.e., the map of transition points, the problem of encoding arbitrary contour maps can be easily converted into a problem of lossless image coding. Experimental results show that the Joint Bilevel Image Experts Group (JBIG) image coding standard can be used successfully for encoding maps of transition points, outperforming, in most cases, differential chain-coding. Moreover, if we take into account that JBIG codecs are available as "off-the-shelf" components, then the effort required to implement the proposed method is small.

Encoding of line drawings with a multiple grid chain code

The multiple grid(MG) chain code which uses four different square grids is proposed to encode line drawings. The main processes adopted in the code are: 1) a grid selection algorithm which allocates quantization points only to the vicinity of the course of a line drawing, 2) labeling rule on quantization points which makes the frequency of some codes larger than that of other codes, and 3) quantization points allocation-not to the corners, but to the sides of a square which makes the straight line segments larger without increasing quantization error. A performance comparison of various chain codes is made from the viewpoints of the encoding efficiency, naturalness of the encoded lines, and the rate distortion measure. Also, the superiority of the MG chain code to other codes is shown. At last, application of the MG chain code to the electronic blackboard system is explained.